Neuroimaging of Anesthetic Modulation of Human Consciousness

Administering anesthetic drugs to suppress consciousness is an imperatively important step in
major surgical operations. Yet the neurobiological mechanisms that underlie loss of
consciousness under general anesthesia remain elusive. Despite advancements in understanding
the molecular, synaptic, and cellular effects of anesthetics, the large-scale, systems-level
modulation of neuronal processes that support conscious cognitive functions is incompletely
understood. While profound decreases in global and regional brain metabolism, blood flow, and
functional connectivity have been reported, these changes often fail to correlate with the
loss and return of consciousness. To date, there is no "consciousness meter" or "gold
standard" to objectively assess and monitor the level of consciousness under general
anesthesia. Several studies suggest that residual cognitive functions may not completely
vanish under general anesthesia; however, the level and complexity of residual information
processing in the anesthetized brain remains unknown. Finally, the neurobiological mechanisms
that govern anesthesia induction and emergence appear to be partially different, but the
relevance of these differences to the modulation of the state of consciousness is unclear.

Inclusion Criteria:

1. Must have a body mass index (BMI) less than 30.

2. Must be right handed

3. Must be English speaking

4. Must be capable of giving written informed consent.

5. Must have history of playing tennis (or any type of racquet sport) at least 30 times
over lifetime.

Exclusion Criteria:

1. History of obstructive sleep apnea;

2. History of a difficult airway with a previous anesthetic;

3. History of neurological disorders;

4. Hypertension or other cardiovascular abnormalities;

5. Pulmonary hypertension or other pulmonary abnormalities;

6. Gastroesophageal reflux disease (GERD) or heartburn;

7. History of significant head injury with loss of consciousness;

8. Learning disability or other developmental disorder;

9. Allergic reactions to eggs;

10. Pregnant or nursing mothers;

11. Contraindications to neuroimaging methods;

12. Inability or unwilling to fast, or withhold food and liquid intake, for 8 hours prior
to your scheduled study visit.

13. Unwilling to abstain from alcohol use for 24 hours prior to your scheduled study
visit.

14. History of drug use, or have a positive drug screen.

15. Tattoos on the head or neck region - all other tattoos are subject to determination by
investigators.

16. Any impairment, activity or situation that in the judgment of the study coordinator or
Principal Investigators would prevent satisfactory completion of the study protocol.